Exogenous melatonin mitigates salinity‐induced damage in olive seedlings by modulating ion homeostasis, antioxidant defense, and phytohormone balance

Abstract

Melatonin (MEL) is a ubiquitous molecule with pleiotropic roles in plant adaption to stress. In this study, we investigated the effects of foliar spray of 100 and 200 μM MEL on the biochemical and physiological traits linked with the growth performance of olive seedlings exposed to moderate (45 mM NaCl) and severe (90 mM NaCl) salinity. Both salt stress conditions caused a considerable reduction in leaf relative water content and the contents of photosynthetic pigments (carotenoids, chlorophylls a and b, and total chlorophylls), K+ and Ca+2, while the contents of Na+ and the activities of antioxidant enzymes increased. In addition, salt‐stressed olive seedlings showed high accumulations of hydrogen peroxide (H2O2), malondialdehyde (MDA), and electrolyte leakage (EL), indicating that olive seedlings suffered from salinity‐induced oxidative damage. In contrast, MEL application revived the growth of olive seedlings, including shoot height, root length and biomass under salt stress conditions. MEL protected the photosynthetic pigments and decreased the Na+/K+ ratio under both moderate and severe salt stresses. Furthermore, MEL induced the accumulations of proline, total soluble sugars, glycine betaine, abscisic acid, and indole acetic acid in salt‐stressed olive seedlings, which showed a positive correlation with improved leaf water status and biomass. MEL application also increased the activities of catalase, superoxide dismutase, ascorbate peroxidase, and peroxidase in salt‐stressed seedlings, resulting in lower levels of H2O2, MDA, and EL in these plants. Taken together, MEL mitigates salinity through its roles in various biochemical and physiological processes, thereby representing a promising agent for application in crop protection.

Physiological mechanisms of ABA-induced salinity tolerance in leaves and roots of rice

“…Conversely, our results showed that salt stress showed a greater increment in ACC, IPA, IAA and ABA in leaves of Chaoyouqianhao, whereas only the increased ABA content was observed in Huanghuazhan. Similar results were obtained by Zahedi et al, who reported that IAA and ABA contents increased in the presence of salinity in olive seedlings 75 .…”

Crosstalk between Melatonin and Reactive Oxygen Species in Plant Abiotic Stress Responses: An Update

“…Salinity stress is one of the serious threats to crop growth and development. Many studies indicate that melatonin enhances tolerance to salinity stress in various plant species, including Arabidopsis , Brassica napus , rice, wheat, tomato, cucumber, Malus domestica , Limonium bicolor , sunflower, and olive [ 12 , 35 , 36 , 40 , 42 , 47 , 53 , 54 , 55 , 56 , 57 , 58 , 59 ]. Within these studies, melatonin regulated ion homeostasis, especially Na + and K + homeostasis, thus alleviating the salinity damage.…”

Transcriptomic Profiling Provides Molecular Insights Into Hydrogen Peroxide-Enhanced Arabidopsis Growth and Its Salt Tolerance

“…Seedling treatment with inorganic and organic agents greatly reduces the detrimental effects of stress and enhances essential nutrient content ( Qiu et al, 2014 ; Cantabella et al, 2017 ; Ghassemi-Golezani and Farhangi-Abriz, 2018 ; Silva et al, 2020 ; Zahedi et al, 2021 ). In our present work, the pretreatment of seedlings with H 2 O 2 increased the fresh and dry weights of salinity-treated seedlings.…”

“…Previous studies on different plants have given controversial conclusions ( Qiu et al, 2014 ; Song et al, 2021 ), which means the roles of JA in plant salt stress tolerance are sophisticated. In this process, the combined action of JA with other plant hormones, such as ABA, ethylene, auxin, and salicylic acid, plus the regulation of hormonal homeostasis may jointly contribute to plant growth under salt stress ( Raza et al, 2021 ; Zahedi et al, 2021 ; Zhao et al, 2021 ; Zhu et al, 2021 ).…”